Commercial diesel fuels contain impurities that can lead to deposition of solids and gums in engines during fuel combustion. Such engine deposit problems are of greater significance for diesel fuels than gasoline fuels because the diesel fuels generally contain greater concentrations of high molecular weight materials. The thermal breakdown of such materials forms insoluble deposits on the engine that can reduce operating efficiency and, ultimately, can lead to corrosion or blockage of fuel injectors and other critical working elements of an engine. To overcome these problems detergent/dispersant additives such as a polyisobutylene succinimide have been extensively used to reduce deposits formation, whereas as a hydrolysed polyisobutylene succinic acid is used to reduce corrosion.
Furthermore, Global legislation towards a reduction of certain components of exhaust emissions, including NOx (nitrogen oxides) and particulate matter such as soot and oxides of sulphur, produced by automotive engines has resulted in a decrease in the sulphur content of fuel such as diesel fuel and gasoline since the sulphur upon combustion produces highly acidic products and can interfere with the functioning of exhaust after-treatment devices of internal combustion engines. In many countries the sulphur content of fuel has been or is being decreased to less than 50 ppm and newer fuels have even lower sulphur contents of 20 ppm or less. Fuels with a sulphur content of 20 ppm or less are often referred to as ultra-low sulphur fuels.
Furthermore in an attempt to meet emissions targets, automotive manufacturers are developing exhaust after-treatment devices to further reduce emissions. These exhaust after-treatment devices are known to be susceptible to sulphur poisoning even at low sulphur concentrations from sulphur-containing components evolved during fuel combustion. As a consequence of sulphur poisoning, exhaust after-treatment devices may be less efficient which can decrease the performance of the engine and can increase the amounts of regulated components, such as NOx and particulate matter and hydrocarbons and carbon monoxide, emitted from the exhaust of the engine. It is known that the preparation of a succinimide dispersant/detergent can be done in the presence of a medium including an aromatic solvent or diluent, such as, xylene or toluene or a 100 Neutral mineral oil. However these mediums generally have low flash points and compositions and processes using such mediums are usually limited to lower processing temperatures and have increased flammability risks. In principle higher molecular weight aromatic compounds with higher flash points may be used. However, many of these aromatic compounds have toxicity issues such as being carcinogenic.
Duncan et al. in International Publication No. WO 02/06428A1 disclose an additive composition for improving middle distillate fuel oils that comprises a hydrocarbyl-substituted monosuccinimide dispersant and an oil having a viscosity at 40° C. of 100 to 400 centistokes.
U.S. Pat. No. 5,241,003 discloses the production of an ashless dispersant formed from a substituted acylating agent. The substituted acylating agent is derived from an acylating agent and a polymer wherein the mole ratio of acylating agent to polymer is at least 1:1. The acylating agent if further reacted with an amine or an alcohol in the presence of diluent mineral base oil.
International Application WO 04/065430 discloses a method of preparing a reaction product of a polyolefin polymer having at least 20 carbon atoms with an acid or anhydride or their esters or combinations thereof having a color on the Gardner Color scale of 3 or less and optionally further reacted with an amine or alcohol in the presence of a diluent oil. The acid or anhydride to polyolefin is less than 1.3:1.
It would be advantageous to have a method of preparing an additive with at least one property of corrosion reduction, dispersancy or detergency. The present invention provides such a method.
It would also be advantageous to have an additive capable of imparting at least one of improved fuel economy, a homogeneous air/fuel mix, nozzle cleanliness, injector cleanliness, improved handling, a final product with a higher actives content in a medium substantially free of to free of sulphur i.e. more concentrated and a low sulphur content into a liquid fuel or an oil of lubricating viscosity. The present invention provides such an additive.
It would also be advantageous to have an additive derived from a compound with a concentration of acylating agent during manufacture which when combined with medium substantially free of to free of sulphur produces at least one of improved fuel economy, a homogeneous air/fuel mix, nozzle cleanliness, injector cleanliness, improved handling. The present invention provides such an additive